Barcode Plugin Development

This article is part of the Ongoing Discussions series.

Installation • Usability • MacOS • Fonts • Other

The barcode plugin does not currently provide all of the functionality that is available in the underlying library, Barcode Writer in Pure PostScript (BWIPP).

This page is intended to provide a collaboration point to coordinate improvements to the barcode plugin. Please extend, debate and discuss as appropriate.

Simple tasks

• Switch from the monolithic flavour of BWIPP to the monolithic-package flavour which is functionally equivalent, more suited to distribution and DSC-conforming. Has been tested by replacing the existing barcode.ps and works as expected. Description of the available flavours here.
• Hexify the data and options string input from Scribus to BWIPP to prevent PostScript injection by means of unescaped ")" or otherwise. See this discussion here.
• Add an advanced checkbox that allows the user to directly provide the options string to the library for advanced users who follow the BWIPP reference.

Moderate tasks

• Add support for the remaining barcode symbologies supported by BWIPP: ISMN, ISSN, GS1 DataBar barcodes, SSCC-18, EAN-14, GS1 Composite barcodes (EAN/UPC, GS1 DataBar and GS1-128), Data Matrix, GS1 DataMatrix, Aztec Code, PDF417, MicroPDF417, MaxiCode, Codablock F, Code 16K, Code 49, Code One, USPS PLANET, USPS Intelligent Mail, USPS FIM, Royal Mail, Royal TNT Post, Japan Post, Australia Post, Deutsche Post Identcode, Deutsche Post Leitcode, Pharmacode, Two-track Pharmacode, Code 32, Pharmazentralnummer, Code 39 Full ASCII, Code 93, Code 93 Full ASCII, Code 11, Codabar, Telepen, Channel Code, PosiCode, BC412, HIBC barcodes.
• To make the presentation of the list of barcode formats manageable we should sort the list of barcodes in the same/similar way as the web-based generator here.
• Use the BWIPP error reporting mechanism to provide specific error messages to users so that they understand why a give input is invalid. For example, the following PS procedure can be used to invoke barcode.ps and on error will halt GS with the descriptive text of the error (e.g. "BWIPP ERROR: EAN-13 must be 12 or 13 digits") sent to STDERR:

 %!PS
 errordict begin
 /handleerror {
   $error begin
   errorname dup length string cvs 0 6 getinterval (bwipp.) eq {
     (%stderr) (w) file
     dup (\nBWIPP ERROR: ) writestring
     dup errorname dup length string cvs writestring
     dup ( ) writestring
     dup errorinfo dup length string cvs writestring
     dup (\n) writestring
     dup flushfile end quit
   } if
   end //handleerror exec
 } bind def
 end
 % If necessary, set up anything specific to the environment here.
 (barcode.ps) run

• Allow the location of the barcode.ps file to be configured by the user so that non-admins users can provide a local version and distributions that deprecate bundled libraries can provide a separately packaged version. A possible search order that achieves this:

1. User defined location specified via some dialog (PATH_TO_BARCODE_PS=USER|DEFAULT), if set to USER, otherwise:
2. ~/.scribus/plugins/barcode.ps
3. [APP_INSTALL_DIR]/share/scribus/plugins/barcode.ps
4. /usr/share/postscriptbarcode/barcode.ps (Fedora's postscriptbarcode package)
5. /usr/share/libpostscriptbarcode/barcode.ps (Debian's libpostscriptbarcode package)

Harder tasks

• Support new barcode formats automatically by scanning the barcode.ps metadata for BEGIN/END ENCODER blocks.
• Extract descriptions, example data and example options from the barcode.ps metadata by scanning for DESC, EXAM and EXOP stanzas within BEGIN/ENCODER ENCODER blocks.

Example barcode.ps metadata for an encoder:

 % --BEGIN ENCODER ean8--
 % --REQUIRES preamble raiseerror renlinear ean5 ean2--
 % --DESC: EAN-8
 % --EXAM: 02345673
 % --EXOP: includetext guardwhitespace
 % --RNDR: renlinear
 ... PostScript resource definition here ...
 % --END ENCODER ean8--

Collaborative tasks

The following require close coordination between Scribus and BWIPP.

• Extend the barcode.ps metadata to describe the options that are available for each encoder so that any frontends such as the Scribus plugin can be light on compiled in data and enhanced by simply replacing the barcode.ps file.